Inductor



Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE INDUCTOR New YorkApplication October 12, 1933, Serial No. 693,387

10 Claims.

My invention relates to inductor structures and more particularly tosuch inductors as are adapted for operation at high and ultra-high radiofrequencies in electron discharge ampliers.

My invention has for one of its objects to provide an improved tuninginductor arrangement forelectron discharge devices operating at high andultra-high frequencies whereby the effective inductance of said inductormay be reduced without generating oscillations in the ineffectiveportion of the inductor.

Still another object of my invention is to provide an improvedrelatively compact tuning inlI'S` ductor for high power amplifiersoperating at high and ultra-high frequencies wherein the convolutions ofthe inductors are arranged to provide for the increased currents flowingtherein as the effective inductance is reduced.

It is a further object of my invention to provide an improved inductorarrangement for pushpull connected electron discharge devices operatingat high and ultra-high frequencies whereby the effective inductance ofsaid inductor may be reduced without generating oscillations in theineffective portions and at the same time, maintaining a high mutualinductance between the effective inductor sections throughout the entiretuning range.

It is a* further object of my invention to provide a relatively compacttuning inductor for push-pull connected electron discharge devicesoperating at high and ultra-high frequencies wherein a high mutualinductance is maintained between the inductor sections, and theconvolutions of the inductors are arranged td compensate for the effectof the increased currents flowing in the circuit as the effectiveinductance of each of the inductor sections is reduced.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My invention,itself, however, both as to its organization and method of operationtogether with further objects and advantages thereof, will be understoodbest by reference to the accompanying drawing in which Fig. 1 disclosesa preferred embodiment of my invention; Figs. 2 and 3 show detailsthereof, and Fig. 4 discloses the electrical circuit of the inductor.

Referring to Fig. l of the drawing, I have illustrated therein aninductor tuning arrangement comprising two like inductors I and 2arranged coaxially and supported by a suitable (Cl. Z50-40) framework 3.The active portions of the inductors I and 2 are adjacent to each otherso that the inactive or ineffective portions of the inductor are at theopposite extremities of the inductor assembly. Each of the inductors Iand 2 is provided with a plurality of taps i and 5 which terminate in aplurality of switch point contacts 6 and 'I. These contacts 6 and 'I aresupported by a pair of insulating strips 8 and 9 fastened upon theinductor frame 3. A switch comprising an arm or bar member Ii! slides inthe space between the insulating members 8 and S, and the bar isprovided with a plurality of switch blades II and I2. The switch bladeII is of suiiicient width to engage two of the contacts 6 and 'I of eachof the inductors I and 2. The purpose of providing such Wide switchblade I I is to maintain a complete short circuit in the ineffectiveportion of the inductor which is adjacent to the effective portion ofthe inductor. The additional switch blade I2 provides an additionalelectrical path through the ineffective portion of each inductor,thereby preventing the ineffective portion from oscillating at someharmonc frequency of the frequency present in the active portion of theinductor.

The manner of mounting the switch may best be seen by referring to Fig.2 which is a cross section of that portion of Fig. l as indicated by thearrows II, wherein it will be noted that the arm or bar member Il) iscompose-d of an insulating material having at the back thereof, aconductance strip i3 to which the switch blades II and I2 are fastenedby means of cap screws. A binding post I4 is in electrical contact withthe conducting bar i3 by means of a spring contact I5.

The switch blades I I and I2 are in continuous contact with the taps atthe remote extremities of the inductors, as will be apparent by anexamination of Fig. 3 which is a cross section of that portion of Fig. 1viewed in the direction of the arrows III, wherein it will be noted thata binding post I4 supports a metallic bus bar I6 as well as the springclip I5. The bus bar I6 is connected electrically by direct contact tothe taps 4 and 5 and the switch points 6 and 'I by means of cap screws.

Reference may now be had to Fig. 4 wherein I have shown the electricalcircuit and the manner in which the inductor may be used. While I haveshown the inductors connected in the output circuits of the electrondischarge devices Il and I8, it is to be understood that a similarinductor arrangement could be suitably used in the input circuit of suchan amplifier. In other words, the adjacent extremities of the inductorsare connected to the input or output electrodes, which may be termed theungrounded electrodes. The anodes of the discharge devices II and IB areconnected to the extremities of the inductors which are adjacent to eachother, and the anode current is supplied from a suitable source througha choke coil I9 which is connected to the taps 4 and 5 which are at theremote extremities of the inductors I and 2. When the switch blade I isat the extreme right position, the blade II rests on only the twocontacts at the extreme right so that both the inductors are at maximuminductance. As the switch arm I0 is moved to the left, the switch bladeII Will first contact the first two pairs of switch points 6 and 'I andfurther motion of the switch will move this switch blade along until ithas reached the fourth and fifth pairs of contacts as counted from theright to the left, whereby at that moment the switch blade I2 will makecontact with the extreme right pair of switch points. It will beapparent that as the switch is moved farther to the left the switchblade I2 provides an additional electric path through each of theineffective portions of the inductors, thereby maintaining variousportions of the inductor at ground potential so as to prevent thegeneration of spurious oscillations within the ineffective portions ofthe inductors. The outputs of the elctron discharge devices I1 and I8are connected to the succeeding circuit through the coupling capacitors2D and 2I. The output circuit is tuned by varying the total effectiveinductance of the inductors and by a variable capacitor 22 connectedbetween the anodes which in conjunction with the inherent capacity 23existing between the adjacent extremities of the inductors, operates todetermine the resonant frequency of the output circuit.

As the switch arm I0 is moved to the left to reduce the total effectiveinductance of the inductors, the resonant frequency of the outputcircuit is increased and at the same time, the radio frequency currentthrough the active portion of the inductors increases in magnitude. Thisincrease in radio frequency current is caused by the increased ratio ofcapacity to inductance in the circuit as the circuit is tuned to thehigher frequencies.

The inductor disclosed in Fig. 1, therefore, is provided withconvolutions which increase in size from the inactive end to the activeend of each inductor. By forming the convolutions of the inductor ofdifferent size conductors, instead of a single size large conductor, itis possible to arrange such an inductor within a very limited space.

While I have shown and described the application of the inductors to aparticular type of amplifier, i. e. a push-pull or balanced amplifier,it is to be understood, of course, that inductors can be usedindividually in amplifiers of the single cascade type. The inductorswhen used individually have the advantages of compact structure, and aplurality of electrical paths in the ineffective portion which preventthe generation of spurious oscillations. While a specific switchingarrangement is shown, it is obvious that any other arrangement could beemployed which would produce the same results.

While I have shown and described my invention in connection with certainspecific embodiments, it Will. of course, be understood that I do notwish to be limited thereto since it is apparent that the principlesherein disclosed are susceptible of numerous other applications, andmodifications my be made in the circuit arrangements and in theinstrumentalities employed without departing from the scope and spiritof my invention as set forth in the appended claims.

What I claim as new and desire to obtain by Letters Patent of the UnitedStates, is:

1. A tuning device for a pair of electron discharge devices, said devicecomprising a pair of inductors arranged coaxially, said inductors havingadjacent extremities connected to the high potential electrodes of saiddischarge devices, and means for reducing the effective inductances ofsaid inductors simultaneously by like amounts, said means operating toproduce a plurality of electrical paths through the other extremities ofsaid inductors thereby to render said other extremities ineffectivewhile maintaining said ad'- jacent extremities effective.

2. A tuning arrangement for a pair of electron discharge devicesincluding a pair of inductors arranged coaxially, said inductors havingadjacent extremities connected to the high potential electrodes of saidelectron discharge devices, a plurality of taps on each of saidinductors, and means for reducing the effective inductances of saidinductors simultaneously by like amounts, said means including aswitching arrangement cooperating with said taps for producing in eachof the opposite ends of said pair of inductors a plurality of electricalpaths thereby to render said opposite ends ineffective while maintainingsaid adjacent extremities effective.

3. A tuning device for a pair of electron discharge devices, comprisingtwo like inductors arranged coaxially, said inductors having activeextremities arranged adjacent to each other and connected to the highpotential electrodes of respective discharge devices, a plurality oitaps on each of said inductors, and means cooperating with said taps forreducing the effective inductances of said inductors by renderingineffective like amounts of said inductors, said means including meansfor short circuiting different unequal portions of each inductor whilemaintaining the adjacent extremities of said inductors active.

4. A tuning device for a pair of electron discharge devices comprising apair of inductors arranged coaxially, said inductors having activeextremities arranged adjacent to each other and connected to the highpotential electrodes of said discharge devices thereby maintaining highmutual inductance between said inductors, a plurality of taps on each ofsaid inductors, and means cooperating with the other extremities of saidinductors and said taps on each of said inductors for rendering saidother extremities ineffective while maintaining the adjacent extremitieseffective, said means including a switch for producing a plurality ofelectrical paths in each of the portions of said inductors to berendered ineffective, said switch including means to short circuit arelatively small portion of each of said inductors immediately adjacentto the effective portions of said inductors.

5. A tuning device for a pair of electron discharge devices comprising apair of inductors arranged coaxially, said inductors having activeextremities arranged adjacent to each other and connected to theungrounded electrodes of said discharge devices, each of said inductorscomprising a helical conductor having larger cross sections at theactive extremity than at the other extremity, and means for renderingineffective like portions of each of said inductors, said meansincluding means for producing a plurality of electrical paths througheach of said ineffective inductor portions thereby preventing thegeneration of oscillations therein.

6. In combination, an inductor coil adapted for operation over a widerange of frequencies, said inductor coil comprising turns of largerdiameter at one end than at the other, means connecting a portion of thecoil at the end having the smaller diameter turns continuously incircuit and for short circuiting unequal portions of the remainder ofthe coil, and means to increase the portion of the coil connected incircuit While maintaining unequal portions of the remainder of the coilshort circuited.

7. In combination, a pair of electron discharge devices connected inbalanced relation, a pair of coaxially arranged inductance coils, saidcoils having adjacent ends connected to the output high potentialelectrodes of said discharge devices, the turns of said coils at saidadjacent ends having dimensions corresponding to the shorter of thewavelengths at which said coil operates, the turns of said coilsincreasingly removed frorn said ends having dimensions differing inaccordance with the increasing Wavelengths at which the coil operateswhen the respective increasingly removed turns are active, and means toconnect together variable points on each of said coils, said pointsbeing equally removed from said ends, and means to short circuit theportion of each of said coils more removed from said adjacent ends thansaid variable points.

8. In combination, a pair of inductor coils arranged in end to endcoaxial relation, the adjacent ends of said coils being connectedtogether through a capacitance resonant therewith, and the outer ends ofsaid coils being connected together to complete an oscillatory circuitcomprising said coils and capacitance, means to excite oscillations insaid coils whereby said adjacent ends oscillate at high potential, andmeans to short circuit portions of said coils remote from said adjacentends while maintaining said adjacent ends active whereby the resonanceirequency of said circuit is varied and close coupling between saidcoils is maintained at the different operating frequencies.

9. In combination, a pair of inductor coils arranged in end to endcoaxial relation, the adjacent ends of said coils being connectedtogether through a capacitance resonant therewith, and the outer ends ofsaid coils being connected together to complete an oscillatory circuitcomprising said coils and capacitance, means to excite oscillations insaid coils whereby said adjacent ends oscillate at high potential, theturns of said coils near said adjacent ends having dimensionscorresponding to operation at high frequencies and the dimensions of theturns of said coils increasingly removed from said adjacent endsdiifering in accordance with operation at lower irequencies.

10. In combination, a pair of inductor coils arranged in end to endcoaxial relation, the adjacent ends of said coils being connectedtogether through a capacitance resonant therewith, and the outer ends ofsaid coils being connected together to complete an oscillatory circuitcomprising said coils and capacitance, means to excite oscillations insaid coils whereby7 said adjacent ends oscillate at high potential, andmeans to short circuit portions of said coils remote from said adjacentends while maintaining said adjacent ends active whereby the resonance:tre-

quency of said circuit is varied and close couf pling between said coilsis maintained at the different operating frequencies and in balancedrelation with respect to ground, and means to short circuit unequalportions of each of said coils removed from said adjacent ends whilemainm taining said adjacent ends active, whereby the frequency at whichsaid circuit operates is varied while close coupling between said coilsis maintained at all operating frequencies.

EDWARD A. LEACH.

